The zebrafish is a powerful model for the study of hematopoietic stem and progenitor cells (HSPC). We have developed a novel HSPC-specific transgenic line (Runx1+23:GFP). We have used this line in time-lapse live imaging studies to track the migration of HSPC during development. We have also performed a chemical genetic screen to find small molecules that modulate HSPC numbers during development. Treating embryos from 2-3 days post fertilization (2-3 dpf) then fixing for in situ staining with HSPC probes cmyb and runx1, we found the compound lycorine increased HSPC numbers. Applying this compound during time-lapse live imaging showed increased accumulation of Runx+ HSPC in the caudal hematopoietic tissue (CHT). Treatment from 2-3 dpf, then washing off the compound, had a sustained effect on the size of the HSPC with Runx+ numbers higher at 5 and 7 dpf.